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-   -   How to use an oscilloscope (http://www.diyaudio.com/forums/equipment-tools/20271-how-use-oscilloscope.html)

SimontY 14th September 2003 04:07 PM

How to use an oscilloscope
 
Hi everyone,

A friend just bought a 1970s oscilloscope for £5 - partly, he was thinking of me and my hi-fi habit!

Neither of us really have much clue about how to use it properly though. Can anyone explain the basics for trying to look at power supply line noise and ripple, or anything else that is useful to a DIYer/tweaker?

Alternatively, can you point me to a good BEGINNERS guide?

Do I need proper probes for it? It didn't come with any and I am using standard multimeter ones...

The 'scope itself is quite large, uses valves, and has two sets of inputs on the front. I can/will post a picture of it shortly.

I put it onto my homemade 5v psu and have managed to see a sort of lumpy sine-wave - is this AC ripple?


Thanks for any suggestions,
-Simon

SimontY 14th September 2003 04:39 PM

Here is a pic, showing what I found on my 5v psu. I guess the waveform shows AC ripple - I must need more than 5,000uf of smoothing!

How do I go about seeing 'noise'/RF/whatever on the line?

Might the scope not be sensitive enough for this??


-Simon

SimontY 14th September 2003 04:40 PM

2 Attachment(s)
err, picture...

faustian bargin 15th September 2003 06:44 AM

i'm in kindof the same boat as you are. just got a used scope, want to figure it out. (if anyone knows where to find a cheap/free manual for a tek 2215a, lemme know...)

i just found this page on tektronix's website, it should help out a great deal. plus, it's in nice printable pdf format.

XYZs of Oscilloscopes

dig in... (or if you're the corny type: 'scope it out.')

/andrew

Jennice 15th September 2003 07:18 AM

Hi guys,

I'm quite used to oscilloscopes. If you still need a hand after going through the guide in the link (in the post above), let me know :)

Jennice

btw.: To me this doesn't look like ordinary ripple... more like a scope picking up as an antenna (no good connection). Could you please post a new pic of that line distortion, with a description of your horizontal time axis (ms/div) and sensitivity (vertical, mV/div)

SimontY 15th September 2003 12:32 PM

Andrew,

Thanks for the link, I will check it out when I get home tonight...


Jennice,

I will check what settings I used when I get home, again ;)
I think I had sensitivity on 5volts, but I'm not sure, I'll check. Not sure about the time setting... I'll look. Btw I don't think I get anything like that when the probe(s) aren't connected, I think it's somehow coming from my power supply. Why do you want a *new* picure of the distortion? Just as a repeat, for consistency?


Cheers guys,
-Simon

Jennice 15th September 2003 12:46 PM

No, it should only be partially for reproduction/reliability. ItÝ's more the point that it doesn't look like the ordinary PSU hum/niose (unless you're working with a hard load on your PSU). :scratch:

Jennice 15th September 2003 12:49 PM

Ooops... by the way...

You CAN risk getting something like that on your scope if one terminal (active) is connected. In that case, you can experience that the probe acts like an antenne, picking up 50 HZ field from nearby sources, such as your PSU leads or the transformer itself.

Jennice

jackinnj 15th September 2003 12:54 PM

Quote:

Originally posted by faustian bargin


i just found this page on tektronix's website, it should help out a great deal. plus, it's in nice printable pdf format.

XYZs of Oscilloscopes

if you have a rainy afternoon when you can't go out and play, spending time on the TEK website will prove an educational treat --

one important thing on scopes -- don't skimp on probes -- no, you don't have to spend $300 on a probe, but a $40 10X/1X probe will make your measurements more reliable and understandable.

Jennice 15th September 2003 01:46 PM

Jacki,

I agree that probes are a factor, but then again, the submitted scope picture had (as I understood it) a 5 V/div scale, and looking at a (hopefully) low impedance. This should, if everything is hooked up OK, provide a very low sensitivity to noise.

Btw., the scope does not seem to have BNC (shielded) input...


Jennice


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